The present invention relates to a Cu(copper)-base alloy having excellent wear resistance and, more particularly, to a dispersion strengthened Cu-base alloy which is suited for forming a wear resisting layer locally on a metallic base.
Some wear resisting Cu-base materials are heretofore known, including precipitation hardened alloys such as beryllium(Be)-Cu alloys made by adding about 2% of Be to Cu or Cu-Ni(nickel)-Si(silicon) alloys known as the Corson alloy. Other known Cu-base materials are dispersion strengthened alloys which are made by dispersing in a Cu-base matrix dispersion phase particles composed chiefly of hard oxides of Si(silicon), Cr(chromium), Be, Ti(titanium), Zr(zirconium), Mg (magnesium) or Mn(manganese) such as SiO.sub.2, Cr.sub.2 O.sub.3, BeO, TiO.sub.2, ZrO.sub.2, MgO or MnO. The former Cu alloys of the precipitation hardened type are made by precipitating intermediate phases or inter-metallic compounds from the matrix and hardening them through an aging treatment for a long time after a solution heat treatment. On the other hand, the process of making the latter alloys of the dispersion strengthened type is represented by a sintering process in which powder of Cu or its alloy for the matrix and powder of an oxide for the dispersion phase are sintered after they have been mixed and compressed. In another representative process, a material prepared by adding to Cu or its alloy for the matrix a metal more oxidizable than Cu or its alloy and holding the same at a high temperature in an oxidizing atmosphere to diffuse the oxidizing gases inside thereby to generate an oxide phase.
It takes a long time for the precipitation hardened alloy to diffuse in a solid to produce the aging precipitation. This requires an accordingly long treatment at a high temperature which causes problems. For example, the precipitation hardened alloy is difficult to use as a material for large-sized parts and is liable to be subject to strains. In another aspect, the particles to be precipitated in this alloy are as small as several microns at most. No matter how hard they might be, sufficient wear resistance especially resistance to sliding wear cannot be obtained. Better sliding wear resistance will be obtained if the dispersed hard particles have a larger diameter (e.g., 10 to 100 .mu.m). This diameter range is difficult to achieve in the precipitation hardened alloy.
On the other hand, one type of these dispersion strengthened alloys, which is made by the internal oxidation process, is accompanied by solid phase diffusion for generation of the dispersion phase particles. The alloy of this type also requires a long treatment at a high temperature so that it is difficult to apply to large-sized parts and also is not free from strains. The dispersion strengthened alloy made by the sintering process can freely achieve the desired diameter of the dispersion phase particles but requires compression and sintering of the whole material. This makes it difficult to form the dispersion strengthened alloy locally in a member.